Prior art network switches implement table aging. In particular, during a packet processing stage, a lookup is done at certain table. The matched entry in that table is tagged as hit. Entry hit information for all table entries are stored in memory. Either a periodic hardware or software process monitors the entry hit information. An action can be performed if a table entry has not been hit for a period of time. For example, aging of MAC addresses is used to evict and update forwarding table entries. In some other cases, this mechanism can be used for network debugging.
Prior art network switches allocate a fixed set of memory that is used to age out a fixed set of tables. In modern system-on-chip (SOC) designs, area and power budget of embedded memory usually dominates the entire chip budget. As a result, it is critical to efficiently and flexibly utilize the limited memory resources.
Software defined networking (SDN) has emerged as a disruptive innovation to the industry. It advocates separation of control plane and high-speed data plane of network equipment. Control of the network, such as flow management, route update, table aging, is traditionally done in a specialized hardware switch chip. However, in the new era of SDN, these complicated functions are moved into separate controller. Such changes call for a new and different approach for architecture and implementation of the data plane, most notably, network switch chips.